The present invention relates to a lens holder of a stacked lens module and a manufacturing method thereof, being applied to assembling of the stacked lens submodule with the lens holder and suitable for applications in camera lenses, small lenses, and mobile phone lenses.
The optical lens module is a compact optical element in cameras or lenses of camera phones. In practice, the optical lens module is assembled by at least one optical lens. Refer to FIG. 1, an optical lens 20a is made from optical plastic material or optical glass and having an optical surface 21a that generally is a round surface, and an outer periphery 22a around the optical surface 21a that can be round or rectangular. In order to assemble and package the optical lens 20a inside a optical lens module, the optical lens 20a is located and assembled in a holding ring (or holder) 10a to form an optical lens set (or assembly) la while the holding ring 10a is made from metal or plastic material. Thus the lens 20a is aligned with a central axis (optical axis) of the optical lens module. Moreover, by an actuator, the holding ring 10a (or the optical lens set 1a) moves inside the optical lens module so as to achieve zoom in/zoom out, as shown in U.S. Pat. Nos. 7,312,933, 7,095,572, US2007/0024989 and JP3650594.
A conventional way of assembly the plastic material or glass optical lens 20a in the holding ring 10a is shown in FIG. 1. For the purpose of glass optical lens assembly, design a holding ring 10a according to shape of the outer periphery 22a of the optical lens 20a such as round or rectangular shape. Then the optical lens 20a is set into a preset cavity of holding ring 10a for being located, glued the optical lens 20a and holding ring 10a. The glue is UV glue that requires a curing process such as being radiated in a UV curing oven for curing. Due to compact size of the optical lens 20a, the optical surface 21a is easy to get scratched or attach with the glue (flow) when the optical lens 20a is located and assembled by automatic or manual gluing. Thus the processes take time and the yield rate is poor. The curing process of the UV curing glue between the glass lens 20a and the plastic material holding ring 10a is especially difficult. Moreover, the curing in the UV curing oven takes long time and the yield rate is poor. Thus the cost is unable to be reduced, as prior arts disclosed in JP3791615, JP06258562, U.S. Pat. No. 7,224,542 and US 2007/0047109.
A technique that places an insert (metal part) in a mold cavity and then formed an article by injection molding process is so called molding insert injection molding method. The insert is set into a mold cavity of a preset mold. Then inject melt plastic material (or rubber) to fill a preset molding area (mold cavity) and cover whole or part of the molding insert. After cooling and curing, the product is released from the mold. Such manufacturing method is applied broadly in electric elements, connector, mechanical parts and LED, as disclosed in U.S. Pat. No. 5,923,805, TWM313317, and JP07120610 etc. While manufacturing a housing (casing) with plastic material lens by such method, the housing is used as an molding insert and put into a mold cavity. Then a plastic material lens is made by plastic material injection and is integrated with the housing. Or use the plastic material optical lens as an molding insert and the housing is made by plastic material injection and integrated with the plastic material optical lens so as to form an integrated housing with plastic material optical lens, as shown in TW 0528279 and U.S. Pat. No. 6,825,503. Refer to JP62251113, the glass plate is used as a molding insert and is covered by plastic material so as to form a window glass or other parts. Refer to U.S. Pat. No. 6,710,945, by using two injection holes for plastic material injecting, a molded lens and a lens holder are molded by injection sequentially. Or use infrared glass as the molding insert and produce a mount covering the infrared glass by injection molding. Refer to U.S. Pat. No. 7,332,110, in a press molding, the eyeglass frame is used as a molding insert and is placed into a mold cavity. The preform of the plastic material lens is heated to a melt status and then the soft preform is turned into the shape of the cavity by heating and pressing of the mold Thus the preform becomes a lens and integrated with the eyeglass frame to form an eyeglass. However, this press molding approach is unable to be applied to a manufacturing process that integrated the glass lens with the plastic material holding ring. Once the plastic material holding ring is used as a molding insert, the softening point of the optical glass is about 500° C. that is far more higher than the deformation temperature such as 80° C. of the plastic material holding ring. Thus when the temperature of the mold achieves the softening point of the optical glass, the plastic material holding ring has already deformed and unable to be molded. Therefore, the press molding is unable to be applied to mass production of the product that uses a plastic material holding ring as a molding insert and glass as molding material.
In addition, as to manufacturing of the lens module revealed in US2009/0059398, an optical lens, an alignment fixture and a sensor are mounted into a mold and then inject plastic material to form a lens module. Or as shown in FIG. 2, as shown in TWM337077, two optical glass lenses 20b, two light shields 30b, a spacer 40b are used as a molding insert to be mounted into molds 31b, 32b in turn. Then a lens holder together with the above molding inserts being covered form a lens module by plastic material injection molding or press molding. However, such technique is unable to be used in the stacked lens submodule already being assembled. Because the stacked lens submodule is an integrated part and is unable to be released into each single element to be set into a mold. Moreover, the optical axis of the optical lenses 20b, optical elements 30b, 40b (shields and spacer) are difficult to be aligned with one another. It takes time and efforts for alignment of the optical axis and this leads to low production rate and poor precision.
For the purpose of assembly the stacked lens submodule with lens holder to form an optical lens module, due to requirement of high precision of the optical lens modules, the assembly precision between lens holder and stacked lens submodule is needed higher than conventional technique. The alignment precision between the stacked lens submodule and the lens holder affects the image resolution of the lens module. Therefore, there are needs to develop a new technique that mass-produces optical lens modules with higher alignment precision by simplified manufacturing processes.